Allowed U.S. Pat. application Ser. No. 194,984, filed May 17, 1988, to the inventor, and assigned to the assignee of the present invention, describes a novel nonporous membrane material for the removal of hydrocarbons and halogenated hydrocarbons from water. The membrane is capable of removing water and water soluble substances from hydrocarbons and halogenated hydrocarbons at great efficiency. One factor limiting the efficiency of the membrane is the thickness of the membrane as the membrane functions as a diffusion barrier to the water and water soluble substances. Thickness of the diffusion barrier is directly proportional to flow efficiency therethrough.
The allowed U.S. Pat. application Ser. No. 240,632 filed Sept. 6, 1988 to the inventor and assigned to the assignee of the present invention, describes a composite membrane material that combines a nonporous hydrophilic material with a second material having selected permeability to molecules that are soluble in both the membrane materials, but not to water. an extrusion method is also disclosed for forming the composite membrane.
Several factors limit the capacity and efficiency of nonporous cuproammonium membranes. As discussed above, a critical factor is the thickness of the membrane. Balanced against decreasing thickness of the membrane is the structural stability of the membrane to remain intact as an unsupported flat membrane or hollow fiber. The above cited U.S. Pat. application Ser. No. 194,984 discloses unsupported cuproammonium cellulose hollow fibers.
The present invention includes means for providing an ultrathin nonporous membrane, such as a cuproammonium cellulose membrane, which has sufficient structural integrity while being significantly more efficient as a diffusion membrane when compared to a thicker unsupported membrane of the same type.